#!/bin/bash

#

# requires: ...topnm, pnmscale, pnmcomp, ppmntsc, ppmtoy4m, mpeg2enc

#

# video format. pal or ntsc

FORMAT=pal

# target image width/height (taking into account visible screen area)

if [ "$FORMAT" = "ntsc" ]; then

  TW=600

  TH=420

else

  TW=632

  TH=512

fi

TMP=/tmp/image_convert.$$.pnm

IMG=$1

MPG=$2

DIR=`dirname "$MPG"`

if [ ! -d "$DIR" ]; then

  mkdir -p "$DIR"

fi

#

# get the file type and set the according converter to PNM

#

FILE_TYPE=`file -i -L -b "$IMG" 2>/dev/null | cut -f2 -d/`

case "$FILE_TYPE" in

  jpg | jpeg)

  TO_PNM=jpegtopnm

  ;;

  tiff)

  TO_PNM=tifftopnm

  ;;

  bmp | x-bmp)

  TO_PNM=bmptoppm

  ;;

  png | x-png)

  TO_PNM=pngtopnm

  ;;

  Netpbm | pnm | x-portable-pixmap)

  TO_PNM=cat

  ;;

  gif)

  TO_PNM=giftopnm

  ;;

  *)

  echo "filetype '$FILE_TYPE' is not supported"

  exit 1

  ;;

esac

#

# 'chroma subsampling mode' mjpegtools >= 1.8.0

#

SUBSAMPLINGMODE=""

if ppmtoy4m -h 2>&1 | egrep -q "'420mpeg2'"; then

    SUBSAMPLINGMODE="-S 420mpeg2"

fi

#

# extract the image size & compute scale value

#

LANG=C # get the decimal point right

$TO_PNM "$IMG" >$TMP 2>/dev/null

S=`pnmfile $TMP | awk '{ printf "%d %d ",$4,$6 }'`

S=`echo $S $TW $TH | awk '{ sw=$3/$1; sh=$4/$2; s=(sw<sh)?sw:sh; printf "%.4f\n",(s>1)?1.0:s; }'`

#

# now run the conversion

#

if [ "$FORMAT" = "ntsc" ]; then

  pnmscale $S $TMP | \

    pnmpad -black -width 704 -height 480 | \

    ppmntsc | \

    ppmtoy4m -v 0 -n 1 -r -F 30000:1001 $SUBSAMPLINGMODE | \

    mpeg2enc -f 7 -T 90 -F 4 -nn -a 2 -v 0 -o "$MPG"

else

  pnmscale $S $TMP | \

    pnmpad -black -width 704 -height 576 | \

    ppmntsc --pal | \

    ppmtoy4m -v 0 -n 1 -r -F 25:1 $SUBSAMPLINGMODE | \

    mpeg2enc -f 7 -T 90 -F 3 -np -a 2 -v 0 -o "$MPG"

fi

#

# cleanup

#

rm $TMP